/*
 * Copyright 2016 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.handler.codec.compression;

import io.netty.buffer.ByteBuf;

import java.nio.ByteBuffer;

final class CompressionUtil
{

    private CompressionUtil()
    {
    }

    static void checkChecksum(ByteBufChecksum checksum, ByteBuf uncompressed,
            int currentChecksum)
    {
        checksum.reset();
        checksum.update(uncompressed, uncompressed.readerIndex(),
                uncompressed.readableBytes());

        final int checksumResult = (int) checksum.getValue();
        if (checksumResult != currentChecksum)
        {
            throw new DecompressionException(String.format(
                    "stream corrupted: mismatching checksum: %d (expected: %d)",
                    checksumResult, currentChecksum));
        }
    }

    static ByteBuffer safeNioBuffer(ByteBuf buffer)
    {
        return buffer.nioBufferCount() == 1 ? buffer
                .internalNioBuffer(buffer.readerIndex(), buffer.readableBytes())
                : buffer.nioBuffer();
    }
}
